Photovoltaic half-cell technology improves the energy efficiency of solar panels and reduces the electrical losses associated with partial shading and local faults.
The problem of shading
In a traditional solar panel, each solar cell is connected in series, so the current generated by each cell must pass through all the other cells in the panel. This means that if one cell is shaded or faulty, it affects the whole panel, reducing its overall performance.
The answer: photovoltaic half-cells
Solar cells are the core element of photovoltaic panels: they’re where electricity is generated by the photovoltaic effect. Half-cell technology involves dividing each solar cell into two parts, usually by cutting the cell in half symmetrically. These half-cells are then connected in series and parallel to form a solar panel. This configuration alters the way current flows through the solar panel, minimizing the impact of shaded or faulty cells on overall panel performance.
By dividing the cells in half, we also reduce the internal resistance of each half-cell, which translates into lower Joule-effect electrical losses. In addition, half-cell solar panels are more temperature-tolerant and reduce the risk of hot spots, helping to extend their lifespan.
Implementation difficulties
Photovoltaic half-cell technology presents several challenges and difficulties related to its implementation:
- Manufacturing complexity: Precisely cutting photovoltaic cells into two equal halves requires more sophisticated equipment and manufacturing processes. This added complexity can lead to higher production costs.
- Additional electrical connections : Half-cell solar panels require a greater number of electrical connections due to the series and parallel configuration of the half-cells. This can increase the complexity of the solar panel design and the likelihood of electrical failures.
- Thermal management : Although half-cell solar panels offer better temperature tolerance and reduced risk of hot spots, they may require more rigorous thermal management to ensure efficient heat dissipation and prevent damage from overheating.
- Training and expertise: Implementing half-cell technology may require additional training for engineers and technicians responsible for the design, manufacture and installation of solar panels.
Photovoltaic cell technologies
Half-cell technology is mainly applied to crystalline silicon photovoltaic cells, such as monocrystalline and polycrystalline cells. However, it is not generally used for thin-film, heterojunction or multi-junction cells, due to differences in the structure and manufacture of these cell types.
- Thin-film cells: These cells are manufactured by depositing very thin layers of semiconductor materials, such as cadmium telluride (CdTe) or copper indium gallium diselenide (CIGS), on a substrate. Cutting these cells into half-cells is not common practice, as their structure and manufacturing methods are very different from those of crystalline silicon cells.
- Heterojunction cells: These cells combine wide-bandgap semiconductor materials, such as amorphous Si or silicon oxide, with narrower-bandgap materials, such as crystalline silicon. Although cutting into half-cells may be technically feasible, it is generally not practiced due to the complexity of cell structure and manufacturing processes.
- Multi-junction cells: These cells are made up of several layers of semiconductor material, each with a different bandgap to capture different parts of the solar spectrum. Cutting these cells into half-cells is not common practice, due to the complexity of their multi-layer structure and the challenges of managing the electrical connections between the different junctions.
Compatibility with other innovations
Half-cell technology can be combined with other solar panel innovations to further improve performance, efficiency and durability. Here are just a few examples of how half-cell technology is compatible with other innovations:
- Bifacial panels: Bifacial solar panels are designed to capture sunlight on both sides of the panel, thereby increasing their energy output. Half-cell technology can be integrated into these panels to reduce shading losses and improve temperature tolerance. Combining the two technologies creates even more efficient solar panels.
- Tiling Ribbon Technology: This technology aims to eliminate the gaps between photovoltaic cells by using conductive ribbons welded directly onto the cells, thus reducing power losses caused by electrical resistance. Half-cell technology can be combined with Tiling Ribbon Technology to create solar panels with more efficient electrical connections and reduced energy losses.
- PERC (Passivated Emitter Rear Contact) cells feature a passivated rear layer that reduces charge carrier recombination and improves energy efficiency. Cutting these PERC cells in half to create half-cells further reduces power losses due to internal resistance and partial shading. Combined with half-cells, this creates solar panels with greater temperature tolerance, reduced energy losses and improved overall efficiency. Solar panel manufacturers often adopt this combination to bring high-performance, efficient products to market.